The present invention relates to a new and improved disposable urinary pad having high liquid impact capacity, high liquid retention, and allows the skin of the wearer to remain dry.
Disposable absorbent products have been known for some time, including such products as disposable diapers, sanitary napkins, wound dressings, bandages, incontinent pads, and the like. These products incorporate an absorbent batt which is used to absorb and hold or contain body fluids. Initially in many of these products, especially diapers and sanitary napkins, the absorbent batt comprised what is termed "wadding" or plies of tissue. The wadding was disposed between a liquid-impermeable backing and a liquid-permeable facing and the plies of tissue were used to absorb and, hopefully, contain the liquid within the product. A diaper which utilizes such an absorbent batt is disclosed in U.S. Reissue Pat. No. 26,151.
The wadding type of product was replaced, for the most part, by an improved absorbent batt which comprises what is termed "fluffed wood pulp fibers". This absorbent batt comprises a layer of individualized wood pulp fibers with the layer having substantial thickness. A diaper which incorporates such fluffed wood pulp absorbent batt is described in U.S. Pat. No. 2,788,003. This diaper had improved absorbent capacity and somewhat better containment than a diaper using a wadding layer. Also, the fluffed wood pulp layer is quite soft, flexible, and conformable, and, hence, produces an improved diaper over diapers using wadding as the absorbent layer.
Though the fluffed wood pulp absorbent batts have improved capacity, the efficiency with which the capacity is sued in a diaper or sanitary napkin is poor. The reason for this is that the fluid to be absorbed is generally deposited in a localized area within the absorbent batt, and the ability of the fluid to move along the plane of the batt is poor. The fluid tends to follow a radial wicking path and consequently moves to the closest edge of the batt where it generally is no longer contained and the product leaks.
U.S. Pat. No. 3,017,304 discloses an absorbent product which incorporates in the product a densified paper-like layer. This paper-like layer acts as a wick i.e., liquid which is placed on the layer tends to move rapidly along the plane of the layer. When incorporated in combination with fluffed wood pulp fiber, the resultant product uses the absorbent capacity of the fluffed wood pulp much more efficiently. Diapers which incorporate this paper-like layer combined with fluffed wood pulp are disclosed and described in U.S. Pat. Nos. 3,612,055 and 3,938,522. This concept of combining wicking ability, or a capillary skin or layer, with fluffed wood pulp fibers has gained wide acceptance in many absorbent products including disposable diapers and sanitary napkins. Even though these products make much greater use of the capacity of the absorbent batt, they still do not totally contain the absorbed liquid. It is probable that these products will leak before the full capacity of the batt is used for the absorption or, at the very least, before the entire liquid void by the user is absorbed. This is especially true when pressure is placed on the batt while wet. For example, a baby sitting down on a previously wetted diaper will very often cause the batt to leak.
An incontinent adult faces not only the problems of the infant but many other problems. First, the void of an adult generally is much higher in volume than that of an infant. Second, a bulge under clothing is accepted by society for an infant, but the ambulatory adult with an incontinence problem longs for a product which is not visible through ordinary clothing. Third, the proportions and shape of the legs and torso of the adult differs considerably from those of an infant. Therefore, a mere enlargement of an infant diaper, such as that shown in U.S. Pat. No. 4,253,461, is not a satisfactory product.
In both the infant diaper and adult incontinent product marketplace, a product is needed which has a large storage capacity. For instance, shaped containers have been suggested. However, these containers have been substantially rigid, do not stay in place, and are quite uncomfortable. A product with a substantially large storage capacity, with an ability to move liquid away from the void zone, which is disposable, which is comfortable, and which does not show through wearing apparel is needed in the marketplace.
A number of years ago, "superabsorbent materials", i.e., materials which will absorb many times their weight of liquid, were developed. Since the development of such materials, attempts to incorporate them in absorbent products such as diapers to enhance the absorption performance of these products have been made. Theoretically, a minimum amount of superabsorbent incorporated in a product would make that product perform as well or better than the prior art products. Perhaps one of the first products to incorporate such a superabsorbent material in a disposable diaper is disclosed in U.S. Pat. No. 3,670,731. This patent discloses an absorbent dressing comprising an absorbent layer sandwiched between a permeable facing and an impermeable backing sheet. The absorbent layer contains water-insoluble cross-linked hydrocolloid polymer as the superabsorbent material.
Even though superabsorbent materials have been available for some time, they have not gained wide acceptance in absorbent products such as disposable diapers, and sanitary napkins. A primary reason for this lack of acceptance of superabsorbents is failure to develop a product capable of economically utilizing the highly increased absorptive capacity of the superabsorbent material. In order to economically utilize a superabsorbent, the liquid being absorbed must be readily accepted and placed in contact with the superabsorbent material. Furthermore, as the superabsorbent material absorbs liquid, it must be allowed to swell. If the superabsorbent is prevented from swelling, it will cease absorbing liquid. Hence, if the superabsorbent material is to function in absorbent products, such as diapers and sanitary napkins, wherein the liquid to be absorbed is placed in a small void area, the structure of the absorbent layer containing superabsorbent materials must have certain characteristics. Over the years a number of techniques have been disclosed in an attempt to provide structures which make efficient use of the superabsorbent material. Such products are disclosed in U.S. Pat. Nos. 4,103,062, 4,102,340, and 4,235,237. In addition, methods for incorporating superabsorbents into suitable layers or suitable configurations which can be placed in an absorbent product, are disclosed in U.S. Pat. Nos. 4,186,165, 4,340,057 and 4,364,992. To date, none of these products has met with any substantial commercial success.
The present invention provides a new and improved absorbent product which possesses a large storage capacity, which is soft and comfortable, which can be designed so as not to be apparent through normal clothing and which utilizes a substantial portion of the absorptive capacity of superabsorbent materials. In addition, the new absorbent product will contain absorbed liquid even when pressure is placed upon the product during use.